Return-path: Received: from shards.monkeyblade.net ([149.20.54.216]:54547 "EHLO shards.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751948Ab3AJKHd (ORCPT ); Thu, 10 Jan 2013 05:07:33 -0500 Date: Thu, 10 Jan 2013 02:07:29 -0800 (PST) Message-Id: <20130110.020729.1358020934840866117.davem@davemloft.net> (sfid-20130110_110743_979796_44220431) To: sgruszka@redhat.com Cc: netdev@vger.kernel.org, edumazet@google.com, greearb@candelatech.com, bjorn@mork.no, linux-wireless@vger.kernel.org, bhutchings@solarflare.com, mirqus@gmail.com Subject: Re: [PATCH v2] net: set default_ethtool_ops in register_netdevice From: David Miller In-Reply-To: <20130110083641.GA5637@redhat.com> References: <20130108153850.GA10464@redhat.com> <20130109.235738.467651533138068641.davem@davemloft.net> <20130110083641.GA5637@redhat.com> Mime-Version: 1.0 Content-Type: Text/Plain; charset=euc-kr Sender: linux-wireless-owner@vger.kernel.org List-ID: From: Stanislaw Gruszka Date: Thu, 10 Jan 2013 09:36:42 +0100 > On Wed, Jan 09, 2013 at 11:57:38PM -0800, David Miller wrote: >> From: Stanislaw Gruszka >> Date: Tue, 8 Jan 2013 16:38:51 +0100 >> >> > Since: >> > >> > commit 2c60db037034d27f8c636403355d52872da92f81 >> > Author: Eric Dumazet >> > Date: Sun Sep 16 09:17:26 2012 +0000 >> > >> > net: provide a default dev->ethtool_ops >> > >> > wireless core does not correctly assign ethtool_ops. In order to fix >> > the problem, move assignement of default_ethtool_ops to >> > register_netdevice(). This is safe because both register_netdevice() >> > and dev_ethtool() are protected by RTNL lock. >> > >> > Patch is besed on hint of Micha?? Miros??aw. >> > >> > Signed-off-by: Stanislaw Gruszka >> > Cc: stable@vger.kernel.org # 3.7+ >> > --- >> > v1 -> v2: change order of default_ethtool_ops initialization to avoid >> > the problem. Change the subject accordingly. >> >> I don't understand this. Why is the assignment of default_ethtool_ops >> at netdev allocation time not working? Is wireless really not using >> alloc_netdev*()? > > It does. This is done on individual cfg80211 drivers , i.e. on mac80211 > or full mac drivers. After alloc_netdev*() call, some cfg80211 drivers > provide they own ethtool_ops, but some do not. For them, wireless core > provide generic cfg80211_ethtool_ops, which is assigned in > NETDEV_REGISTER notify call: > > if (!dev->ethtool_ops) > dev->ethtool_ops = &cfg80211_ethtool_ops; > > But after Eric's commit, dev->ethtool_ops is no longer NULL (on cfg80211 > drivers without custom ethtool_ops), but points to &default_ethtool_ops. The whole idea is to remove these kinds of NULL tests against dev->ethtool_ops, thus creating the invariant that given any netdev one must never be able to see a non-NULL value there.